Francis b



FRANCIS B. STEVENS, or NEW YORK, N. Y.

BALANGED VALVES.

`Specification of Letters Patent No. 8,004, dated March 25, 1851.

To all 'whom t may concern.' i

Beit known that I, FRANCIS B. STEVENS, of the city, county, and State`of New York, have invented certain Improvements in Balanced Valves;`andI do hereby declare that the following is a full and exact descriptionthereof.

My object is a convenient adaptation to the double acting steam engine,of balanced valves commonly known as the Cornish double beat valves. Forthe balanced spindle valves as commonly constructed are liable to twoobjections: In the first place the valve being formed by two disksconnected by a spindle, the :torce ofthe steam acting against the disksin opposite directions puts a great strain on the spindle; so thatshould it be slightly eccentric the valve will be sprung from the seatand will leak; and in the secondplace the difference of expansionbetween the valve spindle which is completely surrounded by steam, andthe steam chests holding the valves, `which is on the outside exposed tothe atmosphere will also cause the valves to leak. The valves commonlyknown as the Cornish double beat valves are obviously superior inprinciple to the spindle valves just described andhaving been inventednearly a century ago and been in constant use ever` since, it may bepresumed that their general introduction `in the double acting steamengine where balanced valves are used, has been prevented or retarded bythe diiiiculties presented tor their adaptation to that purpose. Thesedifficulties might be of the space occupied,or of the expense, or ofsuch an adaptation as would alter but little the arrangementsof theexisting parts of the engine.`

My'object is to endeavor to arrange these valves in such manner, thatthe advantages To eiect this I arrange the valveson the same level; as`this is the arrangement most generally adopted 1n engines havmgbalanced valves; and I also for the same purpose introduce certainpecularities in the construction ofthe valve, that render it different`from any hitherto in use. I `will now proceed to describe myarrangement zby a reference to drawings, and as I know of no instancewhere the particular variety of Cornish valve that I adopt has been madeor used in this country, and of no work where it is described with afigured reference to drawings, I willalso describe this valve sIo thaktIcan `clearly point out the alterations ma e.

Figure l represents aside view of one of each of the steam and exhaustvalves the 'steam valve being the Cornish valve and the exhaustvalvehaving my improvement. Fig. 2 represents a vertical section of thesame valves both raised ofi their seats, which are also shown insection. Fig. 3 represents a horizontal view of the same valves. Fig 4represents a `vertical section of the side pipes,

steam chests, valves, andvalve seats. Fig. 5 represents a horizontalcross section of the lower steam chest, valves and valve seats taken`through the red line aia-m of Fig. 4f.. Fig.- 6 represents a horizontalview of the lower steam chest. Fig. 7 represents a vertical section ofthe side pipes, taken through the red line g/-y of Fig. Ll: 1

In the drawing figuredas above a is the lower steam chest.

Z) is the upper steam chest. ,c and c are the side pipes leadingrespectively to the` boiler and condenser. l d and Z are the openingsfromthe side pipes into the cylinder nozzles. i e isthe opening into thecondenser.

72., 7L. represents the two. steam valves, dif-i` feringbut little ifany from the Cornish valve.

m and m represents the two exhaust valves, showing the alterations thatI make to, adapt them to the position in which they are placedrelatively to the steam passages.

I will in thefirst place describe the di'erent parts of the Cornishvalve. fand f. are respectively the lower and upperseats, the upper seatbeingformed on the circumference `of aidisk supported by a cross g gcastin the center of the ring forming the lower seat-the valve /L` is formedby a hollow cylinder, the lower part of which `being turned in as shown,forms the valve face e' that rests on the seat and the upper `part `alsoturned in forms the valve facer" that rests on the seat f. c are ribscast on the inside` of the valve to guide it. Z is a cross by `which thevalveislifted by the valve stem. rIhe steam valve kthus drawn anddescribed does not differ materially if in any respect from a Cornishdouble beat valve; and I have been thus particular in describing it, asrI wish to explain the manner in which I alter it; this alterationconstituting the material part of my invention.

It will be observed by a reference to the drawing that the position ofthe exhaust valve with'respect to the steam passages, and also withregard to the direction in which it is opened, is such, thatif it weremade similar to the valve just described the pressure of the steam wouldforce it from its seat. It is necessary therefore, in order that thevalve shall be retained on its seat by theV pressure of the steam, thatthe seat formed on the disk supported by the ribs shall be larger indiameter than the seat that forms the circular opening through which thesteam passes. In order to effect this I attach a ring to the valveforming the bearing for the smaller seat. This ring being smaller indiameter than the disk I also attach a ring to this disk forming thelarger seat. I am thus enabled to put the valve together by slipping thesmaller ring over the disk and then by attaching the larger ring to thedisk, and finally by slipping the valve over the disk and attaching itto the smaller ring.

The faces of this valve having respec* tively the smaller and largerdiameter are represented respectively by n and a resting on the seats 0and o.

79 is the disk supported by the cross g.

The valve I form in two pieces by bolting to it the ring r on the edgeof which the smaller valve face n is shown and the disk I also form intwo pieces, by bolting to the disk p the ring s on the edge of which thelarger valve seat o is shown. To put the valve in its place, the ring rmust first be slipped over the disk p-then the 'ring s must be bolted tothe disk p and finally the remainder of the valve must be shipped overthe disk p and ring s and bolted to the ring r. a is a cross by whichthe valve is lifted by the valve stem.

t t are ribs to guide the valve.

From the position in which this valve m is shown in reference to thesteam passages it will be seen that when the 'valve is closed thepressure of steam will be below the valve and the vacuum will be abovethe valve; it will also'be seen from the construc-V tion of the valvethat it will be held down on its seat by the pressure of steam actingfrom` below.

I do not. claim as my invention, valves having seats of such relativediameters, that they shall be retained thereon by the pressure of steam;but

What I claim as my invention and desire to secure by Letters Patent, is-

In the above description of valve where the disk is held b-y a supportrunning up through the hollow valve, so forming the valve that the upperseat4 shall be larger in diameter than the lower one, by means of thering r attached to the valve and by means of the ring s attached to theseat, or 'i by any means substantially the same; for the purpose ofretaining the valve on its seat by the pressure of steam whenever itspositon or location in respect to the steam passages is such that thepressure of steam is below the valve when closed.

FRANCIS B. STEVENS.

